Method of treating iron and steel workpieces prior to cold working

ABSTRACT

Disclosed is a method for treating iron and steel workpieces prior to cold working. The workpieces are pretreated to a temperature of 50*-150*C. and contacted with an aqueous suspension containing solid lubricants of laminar lattice structure. The parts are simultaneously subjected to relative movement so as to cause intercontact between the parts for a period of time sufficient to permit evaporation of a predominant part of the water in the suspension. The quantity of suspension employed is sufficient to yield 5-50 g. active content/m2 workpiece surface area.

United States Patent 1191 Meyer et a1.

1451 Mar. 11, 1975 METHOD OF TREATING IRON AND STEEL WORKPIECES PRIOR TOCOLD WORKING [75] Inventors: Norbert Meyer, Bruchkobel; Han

Yong Oei, Frankfurt am Main; Werner Rausch, Oberursel; Horst Schneider,Frankfurt am Main, all of Germany [73] Assignee: Oxy Metal FinishingCorporation,

Warren, Mich.

22 Filed: Nov. 5, 1973 21 Appl. No.: 413,102

[30] I Foreign Application Priority Data Nov. 7, 1972 Germany ..2254378[52] US. Cl 72/42, 72/46, 117/109, 148/6.15 R

[51] Int. Cl. B21j 3/00, B05c 3/04, C23f 7/10 [58] Field of Search72/39, 41, 42, 46', 117/D1G. 8, 109; 118/416, 418; 148/6.15 R

[56] References Cited UNITED STATES PATENTS 5/1949 Bramberry 148/6.15 R3/1958 Herman 117/109 2,894,484 7/1959 Kearney 117/109 2,939,809 6/1960Jensen ct al. 148/6.15 R

3,013,892 12/1961 Songas 117/109 3,494,327 2/1970 Pearson 118/4183,507,686 4/1970 Hagenbach 117/109 3,775,323 11/1973 Dubourg 1423/6115 RFOREIGN PATENTS OR APPLICATIONS 1,004,836 9/1965 Great Britain 72/46Primary Examiner-C. W. Lanham Assistant Examiner-E. M. Combs Attorney,Agent, or Firm-Arthur E Kluegel; Richard P. Mueller; B. F. Claeboe [57]ABSTRACT 5 Claims, No Drawings METHOD OF TREATING IRON AND STEELWORKPIECES PRIOR TO COLD WORKING BACKGROUND OF THE INVENTION The presentinvention relates to a method of pretreatment of simply shaped standardparts for chip-free cold working, made of iron and steel, in whichaqueous suspensions are used which contain phosphoric acid suspendedsubstances with laminar lattice structure, such as molybdenum disulfide,graphite, as well as surfactants and, where appropriate, otheradditives. These agents are applied to standard parts under certainconditions of use and certain control specifications.

It is a known practice to use a lubricants for the chipfree cold workingof parts oil-free aqueous dispersions of solid lubricants with laminarlattice structure, for example MoS W8 graphite, with the addition ofinorganic thickening agents, and, when appropriate, other additives ofphosphoric acid, metal phosphates, depolarizers, for example nitrate,nitrite, chlorate, (German Pat. No. 1,103,497). Application is made, forexample, by painting on, spraying on or dipping, followed by drying ofthe film. The indicated procedure is too cumbersome and time-consumingfor use with mass-produced small parts.

Aqueous dispersions which contain phosphoric acid, molybdenum disulfide,organic thickeners and, for example nitric acid in addition, arementioned in British Pat. No. 767,572. The application of the agent tothe surface of the workpiece to be shaped takes place by means ofbrushes, while the additional use of heat will lead to acceleration ofthe reaction and drying of the coating. The use of this method is alsocumbersome and timeconsuming.

A more recent procedure for pretreating small iron parts for chip-freecold working is described in the publication mrv. metallpraxisoberflachentechnik 5, A33-A35 (1972) The workpieces are treated inrotating drums, the contact with solutions being made in that therotating drums are dipped in the various baths. In detail, the procedurecomprises the following steps: cleansing; rinsing with water;phosphatizing, for example with a zinc phosphate solution; rinsing withwater at about 80C.; treatment in a stable aqueous suspension at80-85C., containing molybdenum disulfide, binder and film-forming agent;and rotating the drum in air to dry the parts, with supplementary use ofhot air, when required. The procedure here described yields outstandingforming results, but has the disadvantage that it is cumbersome andtime-consuming, due to the multiplicity of the various steps.

The method according to the invention, compared with the prior art,offers the advantage that, in a very simple application involving onlyone stage, small massproduced parts made of iron and steel cansimultaneously be phosphatized and given a lubricating coating, whilecontrol of the thickness of film, within close tolerances, and itsadaptation to the needs of the particular manner of cold working, arepossible. Further, it is advantageous that no waste water is produced bythe process. Thus, it is a process which does not contribute topollution by creating waste rinse water.

SUMMARY OF THE INVENTION The method, according to the invention, for thepretreatment of simply shaped iron and steel small massproduced parts ofchip-free cold working uses suspensions, in themselves known, whichcontain phosphoric acid, suspended substances with laminar latticestructure, surfactants and, when required, thickeners, as well asdifficultly soluble phosphate-forming cations. It is characterized inthat the scalefree workpieces, at a preheated temperature between 50 and150C., preferably to C, carry out a relative motion with reference toone another in a moving, for example rotating or vibrating, containerand thus are brought into contact with so much aqueous suspension that5-50 g. of active content of the suspension is applied per square meterof workpiece surface. The term active content here means thenon-vaporizable portion of the suspension. Motion in the container iscontinued until the predominant portion of the water has evaporated.

In other words, the improvement comprises preheating the workpieces orparts to a temperature between 50 and C. A relative motion of theworkpiece is then effected so as to cause intercontact of the pieceswhile simultaneously contacting the parts with the above-mentionedsuspension, the active content of the suspension being in the range 5-50g/m of workpiece surface area. The relative motion is continued until apredominant part of the water in the suspension has evaporated.

DETAILED DESCRIPTION OF THE INVENTION The aqueoussuspension which,within the scope of the invention, are used preferably contain so muchphosphoric acid that the relation by weight of H PO H O (0.01-0.25) l.The group of laminar structure pigments includes (among others)molybdenum disulfide, tungsten sulfide, boron nitride and graphite. Theportion by weight of the laminar structure pigment, preferably, isbetween 30% and 99% active content. The surfactants used must be stableto acid and are used to wet the metal and/or pigment surface. They maybe selected from the group of nonionic, anionic, cationic and evenamphoteric surface-active substances. Cationic substances, for exampleoleic acidimidazoline derivatives, have been found to be veryadvantageous.

When thickeners are also used, they can be chosen from the group ofknown inorganic and organic thickening agents. Typical examples arebentonite, finely divided silica, cellulose derivatives,polysaccharides, polyacrylamides and the like. Zinc, calcium, manganese,iron, magnesium and others enter the picture as cations which formdifficultly soluble phosphates. In order better to fix the laminarstructure pigment of the metal surface, it is possible to usefilm-forming products, for example acidstable synthetic resindispersions and water-soluble high molecular organic compounds. Toovigorous evolution of foam during the processs of motion can becounteracted by the use of suitable antifoam agents, for example fromthe group of silicone oils. The suspensions may, in addition, containmeans of enhancing the attack of aqueous phosphoric acid on the steelsurface. These include particularly oxidizing agents, such as nitrates,nitrites, hydrogen peroxide and the like. Small amounts of the morenoble metals, such as copper, nickel and cobalt have similar effects. Itis advantageous to stay within the framework of the following weightpercent concentrations for the suspension to be used in connection withthe invention:

5. 50% MOS: preferably 20-40% 0.5' 14% H PO preferably 4-8% 070%" 2%thickener preferably 0.14% 0.05 1% surfactant preferably 0.l0.6%Remainder water The workpiece used in connection with the inventioninclude for example wire sections, sheet metal disks, blocks, sectionsof rods, cylindrical and rectangular metal parts.

It is important that the surface of the workpieces be free of scale andother hard non-metallic impurities. On the hand, thin films of rust,grease or oil do no harm. Phosphatizing of the parts before making useof the method according to the invention is not necessary, but, one theother hand, also does no harm. The envi- -ronment-friendly processeswhich are suitable for cleaning the workpiece are, particularly,radiation, ignition under protective gas and scouring in drums orvibrating tanks. However, it is also possible to make use of knownpickling processes. The preheated temperature of the parts, as requiredwithin the scope of the in-- vention, namely 50-l50C., preferably70100C., can be attained, for example, by heating in an oven, by washingin hot water, as well as by the action of radiation or hot air.

In order to produce the necessary relative motion of the parts,according to the invention, they are placed, for example, in rotatingdrums, in vibrating troughs or drains. The relative motion can beintensified by incorporating baffles. It is the purpose of thesemeasures that the workpiece will rub together superficially, slide overone another and strike together in the course of the treatment.

The extent of the active content primarily relates to the surface of theworkpieces. But, this may also relate to the weight of the workpieces,if there is any more or less reliable relation between surface andweight. The lower range is used for less severe shaping, and the upperrange for more severe shaping. It was surprising to find that, with themethod according to the invention, the thickness of the lubricating filmis relatively uniform even on all surfaces of non-uniformly shapedworkpieces.

Treatment in the moving tank is carried out in such a way that, at theend, most of the water has evaporated. The energy required to evaporatethe solvent is often furnished adequately by the elevated temperature ofthe parts. Removal of the solvent vapor can be facilitated by blowingair onto or into the contents of the tank. However, it is also possible,by supplementary use of heat as the parts are being treated, to supportthe drying process. For this purpose, warm air, thermal radiation, aswell as feeding heat onto the walls of the tanks, may be used.

Under certain conditions, it has been found to be desirable to add aneutralizing agent to the contents of the tank, some time after additionof the aqueous suspension. In this way, excess unreacted acids areconverted into neutral compounds. These neutralizing agents may, forexample, be: zinc oxide powder, calcium oxide powder, calcium carbonatepowder, magnesium oxide powder, but also neutralizing compounds from thealkali group, for example sodium carbonate, trisodium phosphate, borax.

Within the scope of the invention, it may be advantageous to feed intothe moving tank compressible bodies, in addition to the workpieces.These, for example, may serve to prevent surface damage due too severeimpact, when heavy objects are being treated. in the case ofcompressible bodies, the abrasion of which has a lubricating effect, anadditional advantage is the'incorporation of the fines in thelubricating layer. Compressible bodies with lubricating propertiesinclude. for example, polyethylene, polypropylene, polyamide andpolymeric fluorinated hydrocarbons. The size the number of such bodiesper tank filling depend on the nature of the tank motion and the numberand size of the workpieces. They may be present as relatively largeparticles, but the use of fine-grained material is also possible. Undersome circumstances, this may be incorporated in the lubricant layerwithout further comminution.

Table I shows some typical recipes for suitable aqueous suspensions. Theprocedue, according to the invention, will now be explained, in thelight of some Examples:

EXAMPLE 1 100 kg of scaly steel wire sections, with a diameter of 15 mmand a length of l5 mm also, were first pickled in 15% hydrochloric acidat room temperature for 25 minutes, and thus freed of scale. They werethen rinsed in water and given a second rinse in water at C. In thisway, the pieces gained the necessary preheat temperature.vThey were thentransferred into a cylindrical drum with axis of rotation 45-fromvertical, and g Agent No. l/m of workpiece surface (Table l) was pouredover them. This corresponds to about 39 g active content/m workpiecesurface. The parts were tumbled in a drum for 15 minutes, while the drumturned at 30 rpm. Warm air was then blowing in and tumbling wascontinued for another 5 minutes after which the surface of the workpiecewas free of moisture. The pieces showed a uniform coating of molybdenumsulfide and iron phosphate, which adhered firmly to the metallic base.These pieces were shaped into hollow bodies by the cold flow moldingprocess. The operation proceeded without difficulties, that is withoutthe formation of striations on workpiece or tool.

EXAMPLE 2 100 kg of sheet steel discs, with rust and scale-freesurfaces, but covered with a thin grease film, 80 mm in diameter and 5mm thick, were preheated by immersion in water at approximately 100C.They were then transferred to a vibrating trough and, after the additionof 40 g of Agent No. 7 (Table I) were subjected to vibration. The amountof suspension used corresponded to about 22 g active content per m ofworkpiece surface. The vibration continued for 15 minutes, while warmair was blown over the surface of the parts during the entire time. Heretoo, a firmly adhering phosphate lubricating film was formed by thetreatment, making possible entirely acceptable cold working when theparts were molded into bowls.

Table l PERCENT BY WEIGHT Agent No. 1 3 4 5 6 7 8 MOS, 30 25 25 25 10WS, 30 Graphite 50 30 3 4 8 5 l0 8 6 8 5 2 Surfactant 0.5 0.5 l 0.5 20.5 0.5 0.5 Thickening Agent 0.6 0.6 0.3 1 0.3 0.6 0.3 lAntifoamingPAgent 0.06 0.1 0.05 0. l 0.2 0.06 0. l 0.05 ZincOrthohosphate 1.5 Manganese Ortho-Phos- 2 3 Py h h l5 inc rop osp ateCalcium Phosphate 3 Water Remainder What is claimed is:

1. In a method for the treatment of shaped iron and steel workpiecesprior to cold working, making use of aqueous suspensions which containphosphoric acid, suspended substances with laminar lattice structuresand surfactants, the improvement comprising preheating said workpiece toa temperature between 50 and 150C, effecting a motion of said workpiecesrelative to each other sufficient to cause intercontact whilesimultaneously contacting said workpieces with said suspension havingactive content in an amount of between 5 and 50 g/m of workpiece surfacearea and comprising 550% of a laminar lattice compound, 0.5-14% H PO and005-1 surfactant, and continuing said motion until a predominant part ofthe water is said suspension has been evaporated.

2. The method according to claim 1, wherein the evaporation of the waterout of the tank is supported by an external heat source.

3. The method according to claim 1, wherein the aqueous suspension isfed into the moving tank at room temperature.

4. The method according to claim 1, wherein compressible bodies, forexample made of polyethylene, polypropylene, polyamide, polymericfluorinated hydrocarbons, rubber are added to the moving tank, inaddition to the workpieces.

5. The method according to claim 1, wherein after the aqueous suspensionhas acted on the iron and steel workpieces for sufficient time,neutralizing compounds are fed into the tank.

1. In a method for the treatment of shaped iron and steel workpiecesprior to cold working, making use of aqueous suspensions which containphospHoric acid, suspended substances with laminar lattice structuresand surfactants, the improvement comprising preheating said workpiecesto a temperature between 50* and 150*C, effecting a motion of saidworkpieces relative to each other sufficient to cause intercontact whilesimultaneously contacting said workpieces with said suspension havingactive content in an amount of between 5 and 50 g/m2 of workpiecesurface area and comprising 5-50% of a laminar lattice compound, 0.5-14%H3PO4 and 0.05-1 % surfactant, and continuing said motion until apredominant part of the water is said suspension has been evaporated. 1.IN A METHOD FOR THE TREATMENT OF SHAPED IRON AND STEEL WORKPIECES PRIORTO COLD WORKING, MAKING USE OF AQUEOUS SUSPENSIONS WHICH CONTAINPHOSPHORIC ACID, SUSPENDED SUBSTANCES WITH LAMINAR LATTICE STRUCTURESAND SURFACTANTS, THE IMPROVEMENT COMPRISING PREHEATING SAID WORKPIECE TOA TEMPERATURE BETWEEN 50* AND 150*C, EFFECTING A MOTION OF SAIDWORKPIECES RELATIVE TO EACH OTHER SUFFICIENT TO CAUSE INTERCONTACT WHILESIMULTANEOUSLY CONTACTING SAID WORKPIECES WITH SAID SUSPENSION HAVINGACTIVE CONTENT IN AN AMOUNT OF BETWEEN 5 AND 50 G/M2 OF WORKPIECESURFACE AREA AND COMPRISING 5-50% OF A LAMINAR LATTICE COMPOUND, 0.5-14%H3PO4 AND 0.05-1% SURFACTANT, AND CONTINUING SAID MOTION UNTIL APREDOMINANT PART OF THE WATER IS SAID SUSPENSION HAS BEEN EVAPORATED. 2.The method according to claim 1, wherein the evaporation of the waterout of the tank is supported by an external heat source.
 3. The methodaccording to claim 1, wherein the aqueous suspension is fed into themoving tank at room temperature.
 4. The method according to claim 1,wherein compressible bodies, for example made of polyethylene,polypropylene, polyamide, polymeric fluorinated hydrocarbons, rubber areadded to the moving tank, in addition to the workpieces.